Frequency subdividing system



' July 13,1948. v. H. VCIJGEL v 2,445,161

FREQUENCY SUB-DIVIDING SYSTEM Filed Dec. 28, 1945 1154 7746.6 Cl/PPE/VT WA 77461: z o 0 H E. O

INVENTOR. Vz/e/vo/v V0622 4 ATTORNEY .nate positive signals only;

energy; at its output at one-half the frequency of Patented July 13, 1948 UNITED ig-[ms rrA-TE-NT icence rnnoonnors ixf imnesrs'rnm v I I I I VernonH. 'Vogel, Gedar Rapids, Iowa,- assignor to Collins Radio Company,

a corporation of Iowa Application December 28,

; -9 Claims. (Cli-250-' 36) This inventionrelates. to frequency changing ,systems and more particularly to such systems f adapted to produce an output frequency'which is ,anjintegral sub-multiple or the input frequency.

" In certain .radio signalling systems, it is desirable to have the output frequency different fromthe input frequency but having a definite relation thereto, such for example as a sub-mulgtiple." Also for practical application, it is desirablethat this frequency dividing or converting apparatus consist of a simple'ielectronic circuit 'whichmay be made integral with other appara- .tus.orlwhich may befconstructed as a compact "separate unit.

' r Accordingly, it is a principal object of this in- ;vtentionto provide an electronic circuit adapted to produce electrical energy at its output, at a frequency which isanintegral sub-multiple 'of .gtheinput frequency. v

f It is .anotherlobject. ofthis invention to proyideanelectronic circuitincluding two grid-controlled tubes for receiving-alternating current signals orpulses and which is. so. arranged that conduction through the last grid-controlled tube .'..stagev of the circuit is causedonly ,by..the.alter- .--..-nate.ha1f waves otlikepolarity.

- It is another object of. this. inventionto provide, an.-.electron tube. arrangement .which is so .sarranged and biasedthat it conducts .on alterand thereby produces ...yide. .an electronic frequency sub-divider or fre- 'iquency. conversion. circuit ion-use. in @connection ith variousxtypes oe-radioiand electronic; ap-

,1; paratusawherein the frequency conversion, is acz: complished by; .decreasing the amplitude of the alternate positive ahalf. waves of ialternating current below a predetermined threshold level.

in zO-nel of the-features. ofz-this 'inventionis -.that the conversion of the frequency: of: the:.received alternating current *wavesis accomplished- .by a v1 pair of grid-controlled" electron tubes :-andai'comparatively small number of associated" circuiteelements.

Another feature of-the invention isthe :pro- -vision" of a pair of grid-controlled-tubesthe pri- -'maryfunction of the first being=-the:clipping or of alternate positive alsuppression of the peaks ternating current waves of --energy,"-while'* the intervening "unaffe ted-positive *w-aves cause the second tube to act as a-class C amplifier; there- "byproducing. inthe o tput of the" second *tube a Cedar Rapids, Iowa,

'1945,'==Serial.No. 631,647

'2 v2 substantially.sinusoidal wave of energy which is j at one-halfthe frequency of the input wave. j

" Anotherjfeature relates to a frequency subdivider comprisinga pair of grid-controlled electron tubes-the'first ofwhichactsas a peak-him iter only :on alternate positive half waves "of" an 5 inputfrequency and-the second tubeactsas a "class C amplifier and also serves tov control 1' the; cutoff grid bias of' the first tube.

"'Other'objects, features and adyantagestof this .invention'will. be apparent to those skilled inthe ...art as willbe evident from:

. drawing; ingwhichz' the following descriptions taken in connection with 'the accompanying .Fig. 1 is a circuit diagram em odyingtheprlnciples of this invention. I

Fig; 2 shows thetime'relationship of the-wave forms atyarious places'in the circuit shown-in .Fig. 1.

acts as'a peak limiter Generally; this invention comprises, a :system using "two grid-controlled electron tubes which are operated insuch a way that the first-tube -for clipping alternate posi- "tivejlobes of .the'applied waves, and thesecond tube. 1 Only the unclipped' -tube acts as a class C amplifier and'also con- ,trolstheplate currentconductivity of thefirst alternate positive input .waves-zcause,the amplifier tube to conduct. Associated Withthe amplifier is a high .Q tuned circuit which cooperates with the amplifier to producean output at one-half the frequencyiof flthe input frequency to .rjent energy.

the clipper tube.

Referring now more particularly to Fig. 1'," the .peakr-limiterjtube' I0 and amplifier tube' II are ,preferablyin the form of grid-controlledelectron tubes of any well-known type. Inductance [2 isconnected to a source I of alternatingcrirwhich is transferred by transformer action toiinductance l3. Inductance. l3 and parjjallel-cohnected. condenser" l4 constitute a". tank circuit l.5':which' is tuned to resonate at the freiiquencyiof the source I The output energyis Qta ken iromnterminal Iii- 16 of inductance ll,

. resonate atone half the :which' is coupled by transformer action to'inductance I8; Inductance l8 and its parallel-connected. condenser. 20 constitute the outputytank circuit." Circuitiilil is. tuned by condense'r'20 to frequency to which tank #circuit' I5. istuned: The resonant tank circuit "I9 is :a' very high Q circuit, and as suchwill,

" in the well-knownrnanner, continue to produce -"o'scillations'after the decay of energy flow into 1 git; As the energy alternately flows-or oscillates -from= condenser 20 to inductance l 8, it encounters time causes -the complete aresistance which in class C distorted output wave shape. The operating fre-- dissipation of the energy. is dependent upon the Q of the tank circuit.

Circuit I at one end is connected to plate 2| of tube IIJ through condenser 2'2, and at its other end is connected to the negative or low potential terminal 23 of the system. The cathodes 24 and 25 of tubes I ll and II' respectively are also connected directly to this negative terminal. This negative potential is supplied to terminal 23 from any source of D. C. supply having appropriate potential to furnish the desired cathode bias with relation to the respective grids of This required time tubes I0 and I I, so that tube I I can deliver maxi-v mum output.

A fixed value of negative bias is supplied to the control grid 26 of tube In with respect to its cathode, which grid is connected to terminal 21; It will be clear from the following description that the value of the negative bias supplied to grid 26 may vary over a wide range of values and in some cases may be entirely omitted. The inductances 28 are high frequency choke coils to oppose the .iiow of high frequency currents therethrough. Grid 26 of tube In is coupled to the plate 29 of tube II through the coupling condenser 30. Terminal 3| is connected to a source of high positive D. C. potential suitable for application to the plate 29 of tube II. Terminal 32 is connected to a source of negative: direct current potential such that the negative bias applied to control grid 33 causes tube II to operate as a class C ampliher and deliver maximum output. Condenser 34 is a blocking condenser and insulates the plate 2I of tube II! from the negative D. 0. potential at terminal 32. Condenser 35 is of such valueithat it offers a low impedance path between the negative or low potential side 23 oi the system and the junction of choke coil 28 with tuned circuit I9.

The value of the negative bias applied to grid 33 of tube II with respect to its cathode, in the absence of excitation voltage from source I, isapproximately twice that required for plate current cutoff. Plate current flows only during a fraction of the positive cycle of the signal from source I applied to grid 33. This signal is of suincient positive value to drive tube II to plate'current saturation. Hence tube II operates as a amplifier and as such will produce a quency of source I is however sumciently high so that the fly-wheel action sufiicient to allow the tuned circuit I9 to eliminate this distortion. As

.a result, the output produced is substantially sinusoidal (curve 40, Fig. 2), and of one-half the frequency of the input energy (curves 42,43, Fig. 2).

The tube I0 and its associated circuit suppress alternate. positive lobes of the input voltage and thereby allow the excitation or conduction of tube II tooccurat the desired outputfr-equen-cy. The exact operation of this circuit will be readily understood from the following description of its operation taken in connection with the circuit diagram shown in Fig. l and the curves shown in Fig. 2.

Curve 40 represents the output wave form ap-- pearing across terminals I 6. The pulses 4| represent the plate current present at the plate 29 of tube II which cause the wave 40. The voltage ciu've 42 including thedotted positive lobes 43 represent the input waves from source I. Curve 42 represents the wave form of energy applied to the grid 33 of tube. I I as a result of the clipping action of tube ID. The suppression or cutting-off of the positive lobes generation of the output 43 by tube I0 causes the maximum value of poten tial in these alternate lobes to be insufficient to overcome the negative grid bias applied to grid 33 of tube II via terminal 32. This grid bias is represented by line 44. From these comparative values it is seen that the clipped lobes will not be of sufficient positive potential to remove the cutoff biason grid 33. The clipping of lobes 43 is proportioned so that the voltage 42 exceeds the value of the negative bias represented by dotted line 44, on alternate positive cycles only. These alternate cycles result in plate current conduction of tube II and produce current pulses 4| at the plate 29. The fiiy-wheel effiect of circuit I9 tuned to one-half the frequency of the input voltage 42 causes the output curve 49 to be substantially a sine-wave having a frequency equal to one-half the frequency of the input voltage 42, 43.

The voltage on the grid 26 of tube In consists of the fixed grid bias applied at terminal 2'! and the subdivided frequency voltage fed from plate 29 through condenser 30. During the positive portion of the cycle of voltage 40, grid 26 of tube I 0 is therefore biased positively and thereby offers a low'imped-ance path to the negative side 23 of the system. Condenser 22 has a high re'actance at the input frequency and in conjunction with the plate resistance of tube I0, a voltage dividing action occurs which, in conjunction with the fedback voltage, suppresses or cuts off the positive lobes 43 of the input frequency. During the remaining portion of'the cycle of the output 40 it causes the bias of tube III to be sufiiciently'negative to prevent its conduction, and the input voltage passes to the grid 33 of tube II causing this tube to conduct in the manner previously described. 7

While there has been here described one preferred embodiment, it is understood that various changes and modifications may be made therein without departing from the scope of the invention.

What is claimed is:

1. An arrangement for deriving from an input frequency F an output frequency F/n where n is an integer, comprising a first grid-controlled tube having at least an anode, grid and cathode and having its plate and cathode connected across the source of said input frequency, means normally biasing the grid of said tube to plate current cutoff, a second grid-controlled tube having at least an anode, grid and cathode and having its control grid excited in accordance with the potential variations at the plate of said first tube, means normally biasing said second tube to plate current cutoff in the absence of said excitation, a resonant circuit connected to. the plate of said secondtube and tuned to said frequency F/n, a

connection from said resonant circuit to the grid of said first tube for exciting said grid at said frequency F/n for overcoming the normal plate current cutoff biasof said first tube and thereby causing the peaks of alternate half waves of the input frequency to be clipped below a value requisite to render saidsecond tube plate current conductive.

2. An arrangement for deriving from an input frequency F an output frequency F/n where n is .an integer, comprising a first grid-controlled tube having at least an anode, grid and cathode, a resonant circuit tuned to said frequency F and connected for A. C. only across the plate and cathode of said first tube, means normally biasing the grid of said first tube to plate current cutoff, a second grid-controlled tube having at least an anode, grid and cathode, a condenser coupling thepla'te of said firsttubeto the grid of said second tube, means normally biasing the grid of's'aid second tube to-cause said secondtube to-act-as" a class C amplifier, an 'oscillatorycircuit connected to the plate of said second tube and tuned to said frequency Flu, and a connection from the plate of said second tube to the grid of said first tube for overcoming the cutoff bias on said first tube in consonance with the positiVe half waves of said frequency F/n.

3. An arrangement for deriving from an input frequency F an output frequency F/n, comprising an oscillatory output circuit tuned to said frequency F/n, a first grid-controlled tube having at least an anode, grid and cathode and having its plate excited by the input frequency F, a second grid-controlled tube having at least an anode, grid and cathode and having its control grid excited by said input frequency F, normal negative bias circuits for the grids of both of said tubes, means interconnecting the plate circuit of the first tube with the control grid of the second tube, means interconnecting the plate circuit of the second tube with the control grid of the first tube to cause said oscillatory circuit to be excited substantially only at said frequency F/n, a source of D. C. plate potential connected to the plate of said second tube, said D. C. plate potential being D. C. insulated from the plate of the first tube.

4. A frequency-changing system including an input circuit connected to a source of periodic waves, an output circuit tuned to a frequency which is a sub-multiple of the input frequency, a first grid-controlled tube, a second grid-controlled tube, each of said tubes having at least an anode, grid and cathode, the waves from said input circuit being applied to the grid of the second tub-e and to the plate of the first tube, circuit connections for biassing the grid of the first tube under control of the plate potential of the second tube to cause the first tube to clip the peaks only of alternate positive half-waves of the input frequency applied to the control grid of the second tube, means for applying steady bias to the grid of the second tube with respect to its cathode so that the said second tube is normally at plate current cut-off, and circuit connections between the grid of said second tube and the plate of the first tube to cause the second tube to become plate current conductive in synchronism only with the unclipped peaks of the half-waves from the said input circuit.

5. A system according to claim 4, in which said second tube is biassed to act as a class C amplifier and the plate of the second tube is coupled through a condenser to the grid of the first tube to feed back to the grid of the first tube a positive biassing voltage in synchronism with the alternate positive half-waves of the input frequency. V

6. A frequency-changing system comprising a resonant input circuit for connection to a source of periodic waves, a tunable output tank circuit resonant to a frequency which is a sub-multiple of the input frequency, a first grid-controlled tube, a second grid-controlled tube, each of said tubes having at least an anode, grid and cathode, circuit means for applying the positive halfwaves of the input frequency to the plate of the first tube and to the grid of the second tube, means biassing the grids of both said tubes so that they normally do not pass plate current in the absence of positive half-waves of the input frequency, a circuit connection between the plate of the second tube and the control grid of the first tube for causing-thefir'st tube to clipthe peaks only of alternatev halfswaves of'the input frequency appliedt'dtlie control grid of the second tube while said second tube remains at plate current cut-off during -th'e clippedpeak periods, the la tmen oned. i uit-m h n e fect during the unclipped peaks oftlie. inputywes to overcome the normal plate current cut-01f bias on the grid of the first tube.

'7. A frequency-changing system having an output circuit which is resonant to one-half the input frequency, said system including an input circuit which is resonant to the input frequency, a tunable output tank circuit resonant to a frequency which is a sub-multiple of the input frequency, a first grid-controlled electron tube having at least an anode, grid and cathode, circuit means for causing said first tube to be plate current conductive only during the peaks of the alternate positive half-cycles of the said input frequency, and a second grid-controlled tube having at least an anode, grid and cathode and having its control grid normally biassed as a class C amplifier, and means connecting the grid of said second tube to the plate of the first tube and the plate of the second tube to the grid of the first tube to render said second tube plate current conductive only during the positive cycles of said input frequency, which cycles intervene between the said alternate half -cycles.

8. A frequency-changing electronic circuit, having an input frequency equal to twice the output frequency, input terminals and output terminals, an input circuit coupled to said input terminals and resonant at said input frequency, a tunable output tank circuit coupled to said output terminals and resonant at said output frequency, a grid-controlled electron tube having at least an anode, grid and cathode for clipping the peaks of alternate positive waves of the input frequency, a grid-controlled amplifier tube having at least an anode, grid and cathode and having its control grid coupled to the plate of the clipper tube and to the input circuit, circuit connections for causing said clipper tube to clip a portion of each alternate positive wave of said input frequency, the lastmentioned circuit connections including a connection between the plate of said amplifier tube and the grid of said clipper tube for causing said amplifier tube to be plate current conductive during the unclipped portions of the other alternate positive waves of said input frequency.

9. A frequency sub-dividing arrangement, comprising an input circuit resonant at an input frequency, an output tank circuit resonant at a frequency which is a sub-multiple of the input frequency, a pair of grid-controlled electron tubes for coupling the input and output circuits, each of said tubes having at least an anode, grid and cathode, means connecting the input circuit across the plate and cathode of the first tube and across the grid and cathode of the second tube, circuit connections for normally biassing the grids of both tubes so that they do not pass the plate current, a source of direct current plate potential connected to the plate of the sec-ond tube, a first condenser connected between the plate of the, first tube and the grid of the second tube whereby the plate of the first tube is D. C. insulated from said D. C. source, and a second condenser connected between the plate of the second tube and the grid of the first tube for applying to the grid of the first tube a positive potential in synchronism with alternate positive 8 half-waves of the input frequency to render said D 1 first tube plate current conductive. UNI STATES PATENTS VERNON H. VOGEL. Number Name, Date 2,413,956 Coykendall Jan. '7, 1947 REFERENCES CITED. 1' 5 The following references are ofrecord in the file of this patent: 

